Conventionally, a photodetecting device that includes a photodetecting element such as a photodiode has been proposed. Such a photodetecting device includes, for example, a photodetecting element, a capacitor that accumulates charges depending on an amount of light received by the photo detecting element, a control line, and a transistor. In this photodetecting device, the resetting of charges in the capacitor, and the reading of charges from the capacitor are controlled by a signal passing through the control line (see, for example, WO 2007/145346, and WO 2007/145347).
Besides, it has been attempted to make the photodetecting device applicable to a wide range of illuminance by switching an exposure time (shutter speed) of the photodetecting element. For example, by using a faster shutter speed, the photodetecting device has a wider dynamic range. When a fast shutter speed is used, however, charges sufficient for detecting light are not accumulated in a portion where only a small amount of light is received (in a dark portion), which causes blocked up shadows to occur in an output image. In contrast, when a slower shutter speed is used, blown out highlights occur in a portion where a large amount of light is received (in a bright portion). Thus, only with the adjustment of exposure time, it was difficult to achieve both of a wider dynamic range and an accurate image. To cope with this, it has been proposed to use a driving method for achieving a wider dynamic range in a CMOS image sensor as a kind of a photodetecting device (see, for example, S. Decker et at, “A 256×256 CMOS Imaging Array with Wide Dynamic Range Pixels and Column-Parallel Digital Output”, 1998 IEEE International Solid-State Circuits Conference (ISSCC98) p 176, p 177; and Yoshinori Muramatsu “A Signal-Processing CMOS Image Sensor using a Simple Analog Operation” 2001 IEEE International Solid-State Circuits Conference (ISSCC 2001) p 98).